• 12 to \<18 years of age, weighing at least 40 kg, or ≥18 years of age of any weight at screening.

• Presence of risk factors for progression to severe COVID-19 at the time of screening based on age:

‣ 12 to 49 years of age with at least two risk factors, where one must be moderate immunocompromise;

⁃ 50 to 64 years of age with at least two risk factors;

⁃ 65 to 74 years of age with at least one risk factor;

⁃ For participants 75 years of age or older, there are no requirements related to risk factors.

• The list of risk factors includes:

• BMI ≥30 kg/m2; Current smoker; Chronic lung disease; Cardiovascular disease; Type 1 or Type 2 diabetes mellitus; Mild to moderate renal impairment; Neurodevelopmental disorders; Sickle cell disease; Moderate immunosuppression.

• Confirmed SARS-CoV-2 infection as determined by RAT in nasal specimen collected within 1 day prior to randomization. Initial onset of symptoms attributable to COVID-19 within 5 days prior to randomization and at least 1 of the specified symptoms attributable to COVID-19 present on the day of randomization. Randomization must occur no later than the 5th day, where the onset of symptoms is the first day.

• Participants must be unable or unwilling to take nirmatrelvir/ritonavir.